LG’s current flagship smartphone, the G3, sports a screen running at 2560 x 1440 resolution, which works out to 538 pixels per inch. The pixel density on the G3 is significantly higher than the iPhone 5s resolution of 326 PPI, and it’s even higher than the roughly 450 PPI spec on most Android devices with 5-inch 1080p screens. All things equal, higher resolution screens look better. But at what point does the human eye fail to distinguish between ever-increasing resolutions?

According to LG’s chief research engineer Lim Min-ho, speaking to the Wall Street Journal, the increased resolution of the G3 is noticeable because its target customers — men and women in their 20s and 30s — hold their smartphones at a “distance of 20 to 25 centimeters.”

And using their average eyesight and under the assumption that people look into their smartphones from a distance of 20 to 25 centimeters, we concluded that for this group, a pixel density of between 500 to 550 pixels per inch, or ppi, was the maximum level of resolution they could recognize.

It comes down to how far your hold your phone from your face: After all, when looking at a 1080p television from a few feet away, it looks like one big picture. But if you get up close, it’s easy to see individual pixels. It’s the same on the smartphone: Even a 720p display looks seamless at two feet, but it’s a much different picture when your nose gets closer to the glass. There’s no doubt the LG G3 has an extraordinarily crisp screen, but during typical use, that might not be due to its QHD resolution.

This makes the “20 to 25 centimeters” figure the key part of Min-ho’s quote. Apple calls its high-resolution screens “retina displays” and bragged that you couldn’t see individual pixels when it announced the iPhone 4. But Apple’s calculations assumed that you’d be using the phone about a foot from your face, as opposed to the 7.8 to 9.8-inch range LG is using. It is completely logical that people with 20/20 vision can distinguish more detail at a closer range.

The exact definition of when pixels become indistinguishable is a matter of debate: Glossy magazines and photos have long used a 300 dots-per-inch standard, which is roughly equal to Apple’s arbitrary retina cutoff. Raymond Soneira, Ph.D. and president of DisplayMate, thinks that 477 ppi is the “retina” tipping point at 12 inches, but that figure is still well under the G3’s 538 PPI spec.

So in order to continue touting advances in display technology, LG — one of the world’s leaders in supplying mobile panels — needs to move the goalposts. It’s a lot easier to sell higher resolution (bigger numbers) than equally important advances in color and clarity.

Between 7.8 to 9.8 inches of distance, according to this home theatre calculator, increased resolution at QHD can be noticeable. At 12 inches it’s not. In the same interview, Min-ho said that although LG’s increasing “pixel density may go beyond the limitations of what their eyes can recognize,” he still believes that “people will be able to tell the difference when it comes to detail, like when looking closely into a high-resolution picture.”

I typically use my phone at between 12 and 18-inches from my face, but I’m positive I’ve stuck my nose pretty close to the screen at some point. As QHD displays become more common and they become a major marketing point — Samsung’s Galaxy Note 4 is expected to have one, and Apple’s rumored 5.5-inch iPhone could have a PPI count in the 400-500 range — remember, in order to spot the extra pixels, you’re going to have to get up close and personal.